The Neapolitan area extends, virtually unbroken, from
the Bay of Naples to the Bay of Pozzuoli hosting some
of the most densely populated districts in Europe. The
geological nature of this volcanic territory, and the presence
of three active volcanic zones (Vesuvius, Campi
Flegrei, and Ischia), poses a high risk for all the inhabitants
(1.5 millions) and the tourists. The autochthonous
volcanism in the Neapolitan urban area has been investigated
to fully evaluate the volcanic risk in this urban
environment. That has been made through 40Ar/39Ar elevated
precision dating on samples obtained from eight
volcanic deposits cropping out in the Neapolitan area.
By using this dating technique, it is possible to obtain
radiometric ages with a 2σ less than 1000 years. Instead,
through stratigraphic hypothesis has been only stated
that the volcanism in the Neapolitan urban area started
before the Campanian Ignimbrite eruption (39 ka) and
possibly ended about few thousand years ago with minor
eruptions building small tuff cones. Therefore, there
have been measured, with the high sensitivity MAP216
mass spectrometer, argon isotopes extracted stepwise
thermally from those samples previously irradiated.
Then, from these measurements, the ages were evaluated
in two ways. One way is to plot all the apparent
ages vs the cumulative 39Ar released (Age Spectrum),
to calculate a Weighted Mean Plateau Age (WMPA) with
a 2σ precision. The other way is to plot the 40Ar/36Ar ratio
vs the 39Ar/36Ar ratio on an Isotope Correlation (Isochron)
Plot, to calculate an Isochron Age (IA) with a 2σ
precision. The oldest 40Ar/39Ar predates local tuff cones
above 78.43 ± 0.57 ka ago, and the youngest below
15.56 ± 0.36 ka. These results testify the existence of a
volcanic field in the Neapolitan area active for a much
wider period of time than previously believed.

The Neapolitan area extends, virtually unbroken, from
the Bay of Naples to the Bay of Pozzuoli hosting some
of the most densely populated districts in Europe. The
geological nature of this volcanic territory, and the presence
of three active volcanic zones (Vesuvius, Campi
Flegrei, and Ischia), poses a high risk for all the inhabitants
(1.5 millions) and the tourists. The autochthonous
volcanism in the Neapolitan urban area has been investigated
to fully evaluate the volcanic risk in this urban
environment. That has been made through 40Ar/39Ar elevated
precision dating on samples obtained from eight
volcanic deposits cropping out in the Neapolitan area.
By using this dating technique, it is possible to obtain
radiometric ages with a 2σ less than 1000 years. Instead,
through stratigraphic hypothesis has been only stated
that the volcanism in the Neapolitan urban area started
before the Campanian Ignimbrite eruption (39 ka) and
possibly ended about few thousand years ago with minor
eruptions building small tuff cones. Therefore, there
have been measured, with the high sensitivity MAP216
mass spectrometer, argon isotopes extracted stepwise
thermally from those samples previously irradiated.
Then, from these measurements, the ages were evaluated
in two ways. One way is to plot all the apparent
ages vs the cumulative 39Ar released (Age Spectrum),
to calculate a Weighted Mean Plateau Age (WMPA) with
a 2σ precision. The other way is to plot the 40Ar/36Ar ratio
vs the 39Ar/36Ar ratio on an Isotope Correlation (Isochron)
Plot, to calculate an Isochron Age (IA) with a 2σ
precision. The oldest 40Ar/39Ar predates local tuff cones
above 78.43 ± 0.57 ka ago, and the youngest below
15.56 ± 0.36 ka. These results testify the existence of a
volcanic field in the Neapolitan area active for a much
wider period of time than previously believed.